1. Field of the Invention
The present invention relates to a toroidal continuous variable transmission adapted for the vehicle such automobiles.
2. Description of the Prior Art
The toroidal continuous variable transmission has been well known as a type of speed-changing means applicable to the vehicle such as automobiles. Most toroidal continuous variable transmission are in general of at least one toroidal rotary speed changer arranged in-line or tandem array, each of which toroidal rotary speed changers is composed of an input disk driven by an input shaft, an output disk arranged confronting with the input disk and connected to an output shaft, and power rollers arranged in frictional rolling-contact with both the disks. In the toroidal continuous variable transmission, varying the tilt of the power rollers causes the continuous variable variation in the speed of rotation that is to be transmitted from the input disk to the output disk.
Examples of the prior toroidal continuous variable transmissions are disclosed in Japanese Patent Laid-Open Nos. 193454/1989 and 163549/1990.
In most toroidal continuous variable transmissions, when the transmission is in the forward range, the power from the engine is transmitted the output shaft after being always governed at the toroidal speed changers. For the reason described just above, even on driving at a constant speed on, for instance, the motorway for many hours, the power from the engine is transmitted continuously through the toroidal speed changer, irrespective of the speed-changing manipulation being scarcely necessary. This causes a major problem of making less an acceptable service life of the toroidal speed changers. To cope with this problem, a prior toroidal continuous variable transmission, for example, disclosed in Japanese Utility Model Laid-Open No. 60750/1988, has been developed in which a direct clutch is provided to directly couple together the input and output shafts.
Nevertheless, the prior toroidal continuous variable transmission has another aspect of problem in which the direct clutch of a large capacity is inevitably required because the direct clutch is constructed so as to under take entirely the transmission of the whole torque.
In contrast, a improved toroidal continuous variable transmission has been developed to relate to the present invention, wherein a planetary gear mechanism is incorporated between the toroidal speed-changing means and the output shaft so as to share partially the torque to be transmitted. The following will explain a developed toroidal continuous variable transmission with reference to FIG. 2.
Shown in FIG. 2 is a toroidal continuous variable transmission of the type what is called "double-cavity type toroidal continuous variable transmission" in which toroidal speed changers, or 2-set of toroidal speed changers 1, 2, are arranged co-axially in a tandem array on an in-line main shaft 3. The first toroidal speed changer 1 comprises an input disk 4, an output disk 5 arranged confronting with the input disk 4, and power rollers 6 arranged between the confronting input and output disks 4, 5 and making frictional engagement with toroidal or doughnut-shaped surfaces of both the disks 4, 5. The second toroidal speed changer 2, likewise the first toroidal speed changer 1, comprises an input disk 7, an output disk 8 arranged confronting with the input disk 7, and power rollers 9 arranged between the confronting input and output disks 7, 8 and making frictional engagement with toroidal or doughnut-shaped surfaces of both the disks 7, 8. The toroidal speed changers 1, 2 each have two power roller 6, 9 each of which is supported for rotation about its rotational axis 10 while for pivoting movement on a pivotal axis 11 that is perpendicular to the rotational axis, or normal to the plane surface of this paper.
The input disks 4, 7 in the toroidal speed changers 1, 2 may move along the axial direction of the main shaft 3, but rotate together with the main shaft 3 in unison. The power or torque produced by the engine is transmitted through a torque converter into an input shaft 13 that is arranged co-axially with the main shaft 3 in in-line array. The input shaft 13 has at its terminal end a loading cam 14 provided with roller cams 15, the cam motion of which generates a thrust force to urge the input disks 4, 7 against the power rollers 6, 9 in accordance with the amplitude of the input torque, resulting rotating the input disk 4 and further another input shaft 7 through the main shaft 3. It will be thus understood the main shaft 3 serves as the input shaft for the input disks 4, 7. The thrust force is to increase the contact pressure between the power rollers 6, 9 and their associated disks of the input and output disks 4, 7 and 5, 8 to thereby provide the frictional-engaging force that depends on the amplitude of the torque to be transmitted.
The power rollers 6, 9 in the toroidal speed changers 1, 2 are designed for pivoting or rocking movement on their pivotal axes 11 so that the rotation of the input disks 4, 7 may be varied continuously through the power rollers 6, 9 and transmitted to the output disks 5, 8. The power rollers are each mounted on a trunnion, not shown, for rotation as well as for pivoting or rocking movement.
It is to be noted that the rotational axes of the power rollers 6, 9 are coincident with the axis of the main shaft 3. That is, on the neutral position where both the axes of the power rollers and main shaft are on the same plane surface, the power rollers 6, 9 may keep steady their tilt angles corresponding to the neutral position and therefore the ratio of the output speed to the input speed is kept constant. With the movement of the trunnions along the axial direction of the pivotal axes 11 during the transmission of the torque, the power rollers 6, 9 also displace along the axial direction of their pivotal axes 11 whereby the rolling-contact locations of the power rollers 6, 9 with the input and output disks 4, 7 and 5, 8 are deviated from the contact locations at the neutral position. As a result, the power rollers 6, 9 are subjected to the pivotal forces applied from the disks so as to pivot on their pivotal axes 11 with the direction and velocity, which depend on the direction and amount of their displacements along the pivotal axes 11. This pivoting movement of the power rollers 6, 9 causes the variations of the ratio between a radius defined by loci of the rolling-contact locations of the power rollers with the input disks 4, 7 and another radius defined by loci of the rolling-contact locations of the power rollers with the output disks 5, 8 whereby the speed may be variable continuously. The pivoting movement of the power rollers 6, 9 may be adjusted by a controller unit, not shown, which controls the displacements of the trunnions along the pivotal axes 11 through the operation of the actuator so as to attain the desired speed ratio.
The output disks 5, 8 are supported on a connecting shaft 22 through a spline fit or the like so as to turn in unison. The connecting shaft 22 is of a hollow tube in which the main shaft 3 is fitted for rotation relatively to each other and a sprocket wheel 24 is provided integrally midway the tube. The output disks 5, 8 are supported on a casing 25 through bearings, not shown, which may bear both the thrust and radial loads. The power or torque transmitted to the output disks 5, 8 is taken off at a counter shaft 28 through a first power-transmitting means of a chain gearing composed of the sprocket wheel 24, an endless chain 26 and an intermediate sprocket wheel 28 that is mounted to an extremity of the counter shaft 28.
The counter shaft 28 is provided at another extremity thereof with a forward clutch 29 that is drivingly connected at the output side thereof to a gear 30 meshed with a gear 31 fixed to an final output shaft 32 of this power train. The gear train described just above constitutes a gear reduction mechanism and therefore the forward clutch 29 may change the counter shaft 28 and gear 30 from the torque-transmitting phase to the idling phase and vice versa. Combination of the gears 30, 31 also constitutes a second power-transmitting means, or a reverse power-transmitting means, to transmit the rotation of the counter shaft 28 in opposite rotational direction to the output shaft 32. The power train, consisting of the first power-transmitting means of the chain gearing 23, the counter shaft 28 and the second power-transmitting means of gears 30, 31, constitutes a reverse mechanism to transmit the rotation of the output disks 5, 8 to the output shaft 32 in the rotational direction opposite or reversed with each other.
Arranged between the main shaft 3 and the output shaft 32 is a planetary gear system 33 comprised of a sun gear 34 connected to the main shaft 3, planet pinions 36 supported on a planet carrier 35 so as to mesh with the sun gear 34, and an internal ring gear 37 connected to the output shaft 32 so as to mesh with the planet pinions 36. Combined between the planet carrier 35 and the casing 25 is a reverse clutch 38 to shift the planet carrier 35 to the freewheeling phase or the held phase with respect to the casing 25.
A direct clutch 39 is further provided to connect directly the output shaft 32 with the main shaft 3 that functions as an input shaft for the toroidal speed changers 1, 2. The direct clutch 39 is capable of rendering the carrier 35 into the connection with the internal ring gear 37. Engaging the direct clutch 39 causes the carrier 35 to hold the ring gear 37 whereby the main shaft 3 turns together with the output shaft 32 as a unit through the planetary gear system 33.
Operation of the toroidal continuous variable transmission constructed as described above will be explained hereinafter. With driving the engine, the power or torque from the engine is applied through the torque converter 12 to the input shaft 13 and in turn transmitted to the input disk 4 of the first toroidal speed changer 1 through the loading cam 14 and roller cam 15. The rotation of the input disk 4 makes the power rollers 6 rotate and, in turn, the rotation of the power rollers is transmitted to the output disk 5. Concurrently with this, the torque from the input disk 13 is applied through the main shaft 3 to the input disk 7 of the second toroidal speed changer 2. The rotation of the input disk 7 is transmitted to the output disk 8 through the power rollers 9.
On forward driving, the forward clutch 29 is engaged while the reverse clutch 38 is released. In this condition, the counter shaft 28 is in the torque-transmitting phase to the gear 30 while the planet carrier 35 in the planetary gear system 33 is in the freewheeling phase relatively to the casing 25. The rotation of the output disks 5, 8 is transmitted from the connecting shaft 22 to the main shaft 32 through the chain gearing 23 and further in turn the counter shaft 28, forward clutch 29 and gears 30, 31. If the input shaft 13 were rotated in the forward direction, the counter shaft 28 would be rotated in the reverse direction. This reverse rotation is reversed again by the gears 30, 31, resulting in the forward rotation of the output shaft 32. On the other hand, as the reverse clutch 38 is disconnected, the planet carrier 35 is in the freewheeling phase relatively to the casing 25 so that, even if the sun gear 34 drivingly connected to the main shaft 3 rotates, the planetary motion of the pinions 36 may absorb the difference of rotation between the sun gear 34 and the internal ring gear 37 turning together with the output shaft 32.
When the main shaft 3 is connected to the output shaft 32 as in high-speed forward driving, the direct clutch 39 establishes the driving connection of the planet carrier 35 with the internal ring gear 37 of the planetary gear system 33. While the forward clutch 29 shifts the reverse mechanism into the idling phase and the reverse clutch 38 is kept on disengagement, or the planet carrier 35 of the planetary gear system 33 is in the freewheeling phase relatively to the casing 25 of this power-transmitting system. During disengagement of the reverse clutch 38, the engagement of the direct clutch 39 permits the planet carrier 35 to make the torque-transmitting relation with the internal ring gear 37 of the planetary gear system 33. Upon energizing the direct clutch 39, the planet carrier 35 is held in unison with the internal ring gear 37 so that the pinions 36 are held against rotation. By contrast, as the main shaft 3 turns in unison with the sun gear 34 of the planetary gear system 33, the pinions 36 meshed with sun gear 34 rotates in unison with the sun gear 34 to the internal ring gear 37 meshed with the pinions 36 to turn together as an unit. It will be thus understood that the direct clutch 39 connects integrally the main shaft 3 with the output shaft 32 through the planetary gear system 33 so as to establish the direct driving connection between the main shaft 3 and the output shaft 32.
On the reverse range, the reverse clutch 38 is energized whereas the forward clutch 29 is released. The carrier 35 of the planetary gear system 33 is held against the casing 25 so that none of the pinions 39 are driven. The turning of the main shaft 3 may be directly transmitted to the planetary gear system 33 without through the toroidal speed changers 1, 2. The torque in the planetary gear system 33 is applied to the output shaft 32 through the sun gear 34, pinions 36 rotatable only on their own axes, and internal ring gear 37. As the forward clutch 29 leaves the counter shaft 28 and gear 30 freewheeling, the rotational movement of the gears 30, 31 in unison with the output shaft 32 is unobstructive to the rotation of the output disks 5, 8, chain gearing 23 and counter shaft 28. If the input shaft 13, or the main shaft 3, were rotated in the forward direction, the sun gear 34 would be rotated in the forward direction. Nevertheless the planet carrier 35 is kept against rotation and therefore the output shaft 32 is driven in the reverse rotational direction due to the internal ring gear 37.
To change the speed ratio during the output shaft 32 being stalled, the release of the forward clutch 29 may be necessary. As the rotation of the input disks 4, 7 may be transmitted to the output disks 5, 8 through the power rollers 6, 9 with no application of torque to the toroidal speed changers 1, 2, the release the forward clutch 29 makes it possible to cause the power rollers 6, 9 to vary their pivot angles or tilting angles owing to the deviation of the trunnions along the axial direction of the pivotal axes 11. Consequently, even if the landing wheels are locked under such condition that no maximum speed ratio is provided by the toroidal speed changers 1, 2, the power rollers 6, 9 are permitted to adjust their pivot angles or tilting angles so as to attain the maximum speed ratio when idling, so that the vehicle may restart to move.
In the toroidal continuous variable transmission described above, the power or torque from the engine is delivered to the toroidal speed changers 1, 2 through the torque converter 12, input shaft 13 and loading cam 15. The torque, following speed changing to the desired speed ratio, is transmitted to the counter shaft 28 and then to the output shaft 32 through the reduction gear train, or gears 30, 31. In case where no manipulation of speed changing is necessary as in driving at a constant speed on the motorway for many hours, the toroidal continuous variable transmission makes it possible to transmit directly the turning of the input shaft 13 to the output shaft 32 by energizing the direct clutch 39.
In the toroidal continuous variable transmission of the prior type described above, nevertheless, the main shaft 3 and the input shaft 13 are provided separately from each other, the input shaft 13 being provided at the extremity thereof with the loading cam 14 while the main shaft 3 being provided at its extremity with the input disk 4 that is mounted for displacement along the axial direction of the main shaft 3 and against rotation relatively to the main shaft 3. Hence, according to the toroidal continuous variable transmission, even when the power transmission is carried out with the direct clutch 39 energized, it is required to forcibly urge the input disk 4 against the output disk 5 with the strong force in order to attain the reliable transmission of torque from the input shaft 13 to the main shaft 3. That is, on the power transmission with the direct clutch 39 being kept in engagement, the input and output disks 4, 7 and 5, 8 and power rollers 6, 9 in the toroidal speed changers 1, 2 rotate in unison with being subjected continuously to the very strong urging force regardless of nothing to do the power transmission. This results in a problem of making less an acceptable service life of the toroidal speed changers 1, 2. This disadvantage is also true in the prior toroidal continuous variable transmissions of the type, for example, disclosed in Japanese Utility Model Laid-Open No. 60750/1988, other than that described above.
Accordingly, how to eliminate the urging force along the axial direction of the toroidal speed changers with the direct clutch being in engagement has been heretofore recognized as a major problem in the toroidal continuous variable transmission equipped with the planetary gear system.